Research Journal of Applied Sciences, Engineering and Technology 4(17): 2839-2845, 2012
ISSN: 2040-7467
© Maxwell Scientific Organization, 2012
Submitted: November 03, 2011
Accepted: March 30, 2012
Published: September 01, 2012
An Evaluation of the Operation of a Fixed-Time Signalization Scheme for a Four
Leg Intersection in Ilorin Metropolis, Nigeria
Y.A. Jimoh, O.O. Adeleke and A.A. Afolabi
Department of Civil Engineering, University of Ilorin, Ilorin, Nigeria
Abstract: The study reports the assessment of the performance of the signalisation scheme at an urban
intersection with the purpose of reviewing for better and effective management of the junction delays. Maraba
intersection in Ilorin metropolis, Nigeria, is a 4-legged traffic warden controlled intersection in a typical urban
centre of a developing economy with the traffic operating at LOS F at each of the legs. As a result of the
congestion at the intersection and in a bid to ameliorate the frustration experienced by motorists at the
intersection, a fixed-time traffic signalization was installed at the intersection to replace the manual traffic
warden controlled signalization. It was however noticed that the congestion experienced at the intersection has
become worse despite the introduction of the fixed-time signalization. A 4-phase fixed-time traffic signalization
was therefore proposed to replace the present 5-phase signalization, which if implemented will improve the
level of service to D. It was consequently recommended that to achieve the new level of service, the intersection
should be redesigned by increasing the number of lanes from the existing 2 to 3 for two of the legs while the
only approach with a single lane should be increased to 2 lanes.
Keywords: Critical flow ratio, fixed time signalization, intersection congestion, traffic warden controlled
INTRODUCTION
The prevalent method of controlling traffic at
intersections in both medium and small size urban cities,
such as a state capital in developing countries like Nigeria
is the use of human traffic wardens whose operations have
been characterised and found to be comparable to the
automatic signalization for Minna, Niger State (Ndoke,
2006) and cost-effective for Ilorin, Kwara State (Adeleke
and Jimoh, 2011). In the case of the latter, only 3 of the
37 intersections studied were not traffic warden
controlled. However, a major handicap with the traffic
warden controlled signalization, especially at multi-legged
intersections, is the introduction of many signal phases
when it is most convenient to assign exclusive separate
movement phases to each traffic leg and the turning
manoeuvres; which ultimately would result to higher
number of phases than the bench marked number for
optimised efficiency (Federal Highway Administration,
2009).
There are three distinct movement patterns that are
probable at each leg of an intersection, the right turning-,
the through-and the left turning traffic (RT, TT and LT).
It is only the LT and TT traffic that significantly
contribute to safety challenges at the intersections as a
result of conflicts of movement at the space sharing
intersection. The RT movements are free from
interference from the other two movements (TT and LT)
for a right hand side driving practice. Besides the human
element and bias often exhibi table by the traffic wardens,
in-effectiveness in operation and unsafe control at the
intersections are also possible ‘(Adeleke, 2010). Hence in
recent times, automatic traffic signalization control was
introduced by the traffic managers at the major
intersections on the first and second priority arterials in
Ilorin, Nigeria. Maraba intersection was among the
intersections considered where traffic congestion must be
ameliorated to ensure the desirable socio economic
working of the urban city.
It was however observed by the commuters
(including the authors) who frequently ply the routes that
the introduction of the traffic signal at Maraba intersection
has not improved the traffic flow or the operational level
of service at the intersection. The commuters continue to
be burdened with the growing congestion. Consequently,
the study was carried out to evaluate the level of service,
identify the militating problems at the intersection with
the view of designing improvement strategies for a better
service from the signalization.
The objectives of the study were:
C
C
C
Establishment of operating characteristics of the
traffic signalization at Maraba intersection, such as
the signal timing/phases, etc.
Identification of critical lane groups based on the
prevailing flow ratios
Designing an alternative for more effective and
efficient traffic control at the intersection
Corresponding Author: Y.A. Jimoh, Department of Civil Engineering, University of Ilorin, Ilorin, Nigeria
2839
Res. J. Appl. Sci. Eng. Technol., 4(17): 2839-2845, 2012
Table 1: Traffic volume-amilegbe approach
Day
Left turn movement
Through movement
Right turn movement
---------------------------------------------------------------------------------------------------------------------------------------------------------------------------Luxurious
Motor
Luxurious
Motor
Luxurious
Motor
Car
Bus
bus
Truck
cycle
Car
Bus
bus
Truck cycle
Car
Bus
bus
Truck cycle
Monday
5891
1191
12
0
1527
851
20
0
60
645
1782
31
0
18
1636
Tuesday
5900
1391
0
154
1418
856
22
0
16
623
2226
21
0
10
1667
Wednesday 5899
1279
0
148
1420
880
18
0
24
614
2039
19
0
14
1684
Thursday 5721
1191
6
150
1423
799
14
0
14
741
1984
22
0
24
1383
Friday
5734
1220
0
194
1486
609
21
0
40
595
2165
27
0
16
1571
Saturday
5619
1039
15
146
1375
874
20
0
22
581
2218
24
0
42
1477
Sunday
5405
1130
3
104
1551
966
22
0
60
628
2495
38
9
36
1278
Left turn movement: Amilegbe-Sango; Through movement: Amilegbe-Sabo Oke; Right turn movement: Amilegbe-Post office
Table 2: Traffic volume-sango
Day
Left turn movement
Through movement
Right turn movement
---------------------------------------------------------------------------------------------------------------------------------------------------------------------------Luxurious
Motor
Luxurious
Motor
Luxurious
Motor
Car
Bus
bus
Truck
cycle
Car
Bus
bus
Truck cycle
Car
Bus
bus
Truck
cycle
Monday
434
17
0
33
461
4753 257
0
148
1384
4896
1261 0
298
2187
Tuesday
400
12
0
16
86
4897 293
9
180
1424
4949
1082 3
106
1809
Wednesday 411
6
0
14
98
5149 356
0
138
1345
4656
1199 15
250
1870
Thursday 403
10
0
14
89
5030 254
0
118
1368
4840
1287 0
204
1994
Friday
263
9
0
16
70
4787 274
0
110
1213
5075
1046 0
144
2008
Saturday
397
28
0
6
88
4570 208
0
110
1223
4929
1163 0
346
1887
Sunday
598
6
3
0
110
6133 155
6
100
869
4225
1125 12
152
1674
Left turn movement: Sango-Sabo Oke; Through movement: Sango-Post Office; Right turn movement: Sango-Amilegbe
Table 3: Traffic volume-sabo oke approach
Day
Left turn movement
Through movement
Right turn movement
---------------------------------------------------------------------------------------------------------------------------------------------------------------------------Luxurious
Motor
Luxurious
Motor
Luxurious
Motor
Car
Bus
bus
Truck
cycle
Car
Bus
bus
Truck cycle
Car
Bus
bus
Truck
cycle
Monday
160
2
0
0
77
1179
59
0
52
607
1896
62
0
16
288
Tuesday
192
9
0
0
84
1194
52
0
40
617
1672
61
0
22
307
Wednesday 157
8
0
0
84
1205
67
9
70
548
1576
59
0
22
265
Thursday 0
0
0
0
0
1159
49
0
36
639
1816
48
0
14
306
Friday
148
6
0
0
94
1204
72
9
80
580
1583
54
0
4
277
Saturday
1455
34
0
38
827
4309
102
0
168
731
185
0
0
0
116
Sunday
345
8
3
0
123
891
48
0
56
589
680
21
0
42
335
Left turn movement: Sabo Oke-Post office; Through movement: Sabo Oke-Amilegbe; Right turn movement: Sabo Oke-Sango
Table 4: Traffic volume-post office approach
Day
Left turn movement
Through movement
Right turn movement
---------------------------------------------------------------------------------------------------------------------------------------------------------------------------Luxurious
Motor
Luxurious
Motor
Luxurious
Motor
Car
Bus
bus
Truck
cycle
Car
Bus
bus
Truck cycle
Car
Bus
bus
Truck
cycle
Monday
1441
36
0
38
1018
3785
106
3
136
870
149
0
0
0
100
Tuesday
1386
36
0
38
1040
3770
179
3
118
958
137
3
0
2
111
Wednesday 1354
33
0
28
820
4129
108
0
128
925
178
5
0
0
117
Thursday 1249
30
0
32
821
3329
88
0
74
1198
172
0
0
0
79
Friday
1268
42
0
20
1040
4261
119
0
116
845
141
0
0
0
145
Saturday
285
8
0
2
94
1265
53
0
34
604
1392
57
0
26
382
Sunday
1980
44
0
2
187
5508
264
0
100
804
437
18
0
12
209
Left turn movement: Post office-Amilegbe; Through movement: Post Office-Sango; Right turn movement: Post Office-Sabo Oke
Table 5: Peak hour traffic volume, timing and movement at Maraba
Vehicle movement pattern
--------------------------------------------------------Approach
Day and time
LT
RT
TT
Amilegbe
Tue
8-9 am
829
450
164
Sabo oke
Sat
10-11 am
202
42
519
Post office
Sun
6-7 pm
220
60
619
Sango
Mon
10-11 am
68
823
689
LT: Left turn traffic; RT: Right turn traffic; TT: Through traffic
MATERIALS AND METHODS
Project area description: Maraba intersection is located
on the first priority arterial (Spencer et al., 1982) and as
modified by Adeleke (2010) because it connects the
township with a number of priority services of educational
institutions (e.g., Kwara State Polytechnics), health
institution (University of Ilorin Teaching Hospital
Total hourly volume (pcu/hr)
1443
763
986
1580
(UITH)) and the Nigerian National Petroleum Corporation
(NNPC) petroleum depot, Okeoyi. Ilorin metropolis is a
typical medium size urban, administrative and political
headquarters of Kwara State, one of the 36 states in a
developing economy of Nigeria. The intersection is fourlegged with three of the approaches dualised. The
approaches include Post office, Sango, Amilegbe and
Sabo Oke; Sabo Oke being the only approach not
2840
Res. J. Appl. Sci. Eng. Technol., 4(17): 2839-2845, 2012
Table 6: Saturation flow rate computation
Approach
So
N
fw
Amilegbe
1900 2
1
Post office
1900 2
1
Sabo oke
1900 1
1
Sango
1900 2
1
fHV
0.982
0.998
0.977
0.98
fg
0.99
0.99
0.99
0.99
fp
1
1
1
1
fbb
1
1
1
1
fa
0.99
0.99
0.99
0.99
fRT
0.70
0.94
0.95
0.56
fLT
0.97
0.99
0.99
1
S
2483
3431
1711
2044
dualised. The intersection is located in a business district
area and adjoined by a public transit park for the intra-and
inter-city journeys from Ilorin to the northern part of the
nation.
Data collection and analysis: Observatory method of
data collection was used to determine the following
characteristics:
C
C
C
C
Prevailing Level of Service (LOS) at the intersection
Existing signal phasing, cycle length and
identification of critical lane groups
New signal phase design parameters
Checks to ascertain the appropriateness of the
designed signal timing in relation to the HCM
specified LOS criteria.
Traffic count and analysis: A 12 h (7 am to 7 pm)
classified traffic count, junction origin and destination
(O&D) survey and signal phasing studies were conducted
for 7 consecutive days in the month of July 2011 with 3
observers at each approach leg. The acquired data were
used for the determination of the prevailing traffic volume
trend, peak hour timings and flow rate, movement
patterns and the traffic signalization characteristics. The
outcome is summarised in Table 1-4 for Amilegbe,
Sango, Sabo Oke and Post Office legs respectively. Five
different vehicle (carrier) types were observed at the
intersection; motorcycles, passenger cars, mini/midi buses
(12-18 passengers capacity), buses and heavy goods
trucks. The traffic movement scenario at a peak period for
a typical day of the week and corresponding time of
occurrence were analysed and summarised in Table 5.
The maximum hourly volumes, as well as the flow
movement scenarios were considered and used to derive
the critical values of the flow ratio (v/s ratio) for the lane
groups in each signal phase and for each approach. The
critical lane groups were subsequently identified and used
to evaluate the adequacy or otherwise of the existing
signal phasing scheme. The data were also employed to
design an improvement of traffic control at the
intersection. Figure 1 is the schematic diagram of the
intersection and the traffic movement patterns at a typical
daily peak hour on the intersection.
The saturation flow rate for each of the approaches
was obtained using the Highway Capacity Manual model
shown in Eq. (1) (Highway Capacity Manual, 2000). The
results are summarised in Table 6.
S = SO N fw fHV fg fp fbb fa fRT fLT
(1)
Fig. 1:Intersection layout and critical volumes
Fig. 2: Existing phase diagran
where,
S = Total saturation flow rate for lane group (vphg)
So = Ideal saturation flow rate per lane (pcphgpl),
usually taken to be 1900 pcphgpl
N = Number of lanes in the lane group
fw = Adjustment factor for lane group
fHV = Adjustment factor for heavy vehicle presence
fg = Adjustment factor for grade
fp = Adjustment factor for parking conditions
fbb = Adjustment factor for local bus blockage
fa = Adjustment factor for area type
fRT = Adjustment factor for right turning vehicles
fLT = Adjustment factor for left turning vehicles
Determination of critical lane groups and existing
signal phasing: During any green signal phase, several
lane groups on one or more approaches are permitted to
2841
Res. J. Appl. Sci. Eng. Technol., 4(17): 2839-2845, 2012
Table 7: Signal phase, actual capacity and group lanes of maraba intersection ilorin
Critical volume Saturation
Flow
Flow ratio
(max hourly
flow
ratio
for critical
Phase
Movt
volume)(v)
rate(s)
(v/s)
lane group(v/s)cr
1
Left turning movt
829
2483
0.334
0.334
from amilegbe
approach
Through traffic
164
2483
0.066
from amilegbe
2
Through traffic
689
2044
0.337
0.337
from sango
Through traffic
619
3431
0.180
from post office
3
LT from sabo Oke
202
1711
0.118
0.303
4
5
Through traffic
from sabo oke
LT from post office
LT from sango
LT from post office
Through from
post office
C
C
c = sg/C
capacity
of lane group Remarks
604
Not OK/
over saturated
g/C
0.243
604
40
0.216
442
Not OK/
over saturated
742
40
0.216
370
519
1711
0.303
220
3431
0.064
0.064
20
0.108
371
68
220
2044
3431
0.033
0.064
0.180
40
0.216
221
742
619
3431
0.18
Not OK/
over saturated
370
OK/
under saturated
OK/
under saturated
742
move, the lane group with the most intense traffic is
considered as the critical lane. The critical lane groups
obtained for the study by comparing the flow ratio (v/s) of
each lane group, (McShane et al., 1998) during a typical
peak period are summarised in Table 7.
There were five signal phases at the intersection as
displayed in Fig. 2 and shown in Table 7. The actual
capacity (c) of each lane group was compared with the
corresponding critical volume to determine whether or not
the capacity of the lane group can accommodate the
maximum hourly volume (Table 6). The comparison
shows that:
C
Existing
green
time
45
Table 8: Experienced delay and LOS at the intersection for a cycle of
operation
d2
PF
d (sec) LOS
Phase
g
c
X
d1
1
45
604
1.37 105 177
1
282
F
2
40
442
1.56 86
263
1
349
F
3
40
370
1.40 82
196
1
278
F
4
20
371
0.59 79
191
1
270
F
5
40
742
0.83 69
87
1
156
F
Determining existing level of service: In order to
determine the LOS at the intersection, the control delay
(d) at the intersection was computed using Eq. (2) to (4)
(Highway Capacity Manual, 1994). The results are shown
in Table 8.
In Phase 1, the left turn movement has a volume
greater than the capacity of the lane group
Phase 2, all the movements have higher traffic
volume than the actual capacity
Phase 3, the capacity is inadequate for the through
traffic flow
Evaluation of existing signal timings at the
intersection: The signalised intersection has a Cycle
length (C) of 185 sec. The critical lane group flow ratio
(v/s)cr in each phase was identified, summed up and used
for the evaluation of the operational efficiency of the
traffic signalization. If the sum of the critical lane group,3
(v/s)cr is greater than 1.00, then the intersection is
deficient in providing sufficient capacity for the
anticipated or existing critical lane group flows (McShane
et al., 1998); either in the facility geometry, phase plan or
cycle length specified. The flow ratios for the critical lane
groups gave a summation of 1.218 confirming the
inadequacy of the signalised control at the Maraba
intersection. Since 3v/scri value of 1.218 › 1.0, the
geometry is inadequate. A more efficient phase plan and
addition of lanes to critical lane groups would be
necessary to remedy the situation.
d = (d1 * PF) + d2 + d3
(2)
g 2

 0.5 * C(1  C ) 
d1 
 g
1     Min( X ,10
. )
 C
(3)
and

d 2  900T  ( X  1) 

( X  1) 2 
8kIX 

cT 
(4)
where,
d1
d2
d3
2842
= Average delay per vehicle due to uniform arrivals
in sec/veh
= Average delay per vehicle due to random arrivals
in seconds
= Residual delay, sec/veh, accounts for
oversaturation queues that may have existed prior to
the analysis period
Res. J. Appl. Sci. Eng. Technol., 4(17): 2839-2845, 2012
Table 9: Start-up lost time for cycle 1
Cycle 1
--------------------------------------------------------------------------------------Vehicles in platoon vehicle headway (sec) vehicle headway-1.86
1
2.30
0.44
2
2.08
0.22
3
2.30
0.44
4
2.12
0.26
Start up lost time: 1.36 sec
Table 11: Summary of the proposed and existing saturation flows
Existing saturation
Proposed saturation
Approach
flow (pcphgl)
flow (pcphgl)
Sango
2044
3066
Amilegbe
2483
3725
Post office
3431
3431
Sabo oke
1711
3422
L = 2.54+1.41 = 3.95 sec, approximately 4 sec
Table 10: Observed clearance lost time for various cycles
Cycle
1
2
3
4
5
6
7
8
9
10
Clearance 1.20 1.24 1.25 1.51 1.36
1.54
1.85 1.50 1.36 1.26
lost time
(sec)
C
g
X
T
K
=
=
=
=
=
Cycle length in seconds
Effective green time for lane group in seconds
Volume Capacity (v/c) ratio for lane group
Duration of analysis period in h
Delay adjustment factor that is dependent on signal
control mode
I = Upstream filtering/metering adjustment factor
c = lane group capacity, in veh/hr
PF = progression factor
For pre-timed control and for situation where there is
no initial queue at the beginning of the analysis period, PF
= 1.0, K = 0.5, i = 1.0, d3 = 0.
Determination of signalization operational start-up
and clearance lost times: The necessary signal design
and operational properties include the saturation headway,
start-up lost time and clearance lost times which were
determined for the study intersection. The saturation
headway (h) was determined by observing the time
headway (h) of 10 vehicles in the traffic queue. It was
however noticed that the observed headways did not
become constant after the first four or five vehicles as
expected for a traffic platoon at a signalised intersection.
The headway was therefore observed over 10 cycles of
signal operation and the average headway of 1.86 sec for
all the vehicles in the 10 cycles adopted as the saturation
headway. This value of (h) was used to compute the startup lost time from the headway of the first four vehicles on
each platoon of the 10 cycles. The resulting start-up lost
time for cycle 1 is shown in Table 9 while those for other
cycles were similarly determined. The average start-up
lost time (l1) for all the 10 cycles gave a value of 2.54 sec
as shown in Eq. (5):
Average Start up lost time for the 10 cycles =
(1.36+2.19+5.56+3.84+2.68+1.22+1.15+2.57+
2.27+2.52)/10
(5)
=25.36/10
=2.54 sec
Observed clearance lost time is shown in Table 10. The
average observed clearance lost time (l2) is 1.41 s e c .
Thus the total lost time (L) is given as:
DISCUSSION OF RESULTS AND THE NEED
FOR A REDESIGN
Observations: It was obvious from the preceding
portions of the paper that the traffic signal scheme at
Maraba junction, Ilorin is not efficient. There was in
operation a five signal phasing scheme. The volume
capacity ratio was greater than 1 for three of the phases
and with all the phases experiencing level of service F.
The frustration being experienced by commuters at the
junction seems justified. It can therefore be speculated
that the plan of the signal abnitio was not driven by the
traffic operational characteristics. Hence, improvement
strategies must be examined in any or all of the three sub
components of a transportation system; the vehicles
(carrier), the fixed facility and the operational
characteristics (traffic control). The geometry of the fixed
facility and operation (traffic control) aspects were
considered together in the analysis in order to maximise
the benefits derivable from the design.
Evaluation of existing geometry of maraba
intersection: Sango approach with a road width of 10.73
m has 2 lanes in use. Amilegbe approach with a road
width of 10.33 m has 2 lanes in use. The Post Office
approach with a width of 9.5 m has 2 lanes in use while
Sabo Oke, with a width of 7.3 m has 1 lane in use. From
earlier analysis, it was found that 3 v/scri › 1 for the
intersection. A suitable geometric design was therefore
proposed so as to have a 3 v/scri ‹ 1 for all the phases. A
better phasing plan and optimum cycle length were also
tried so as to handle the demand flows and reduce the
delays, respectively.
This involved the addition of one lane to three of the
approaches (i.e., Sango approach, Amilegbe approach and
Sabo Oke approach) with critical lane groups as follows:
Sango approach-3 lanes; Amilegbe approach-3 lanes;
Sabo Oke approach-2 lanes. Post Office approach
maintains 2 lanes because of the high density of physical
development, the cost of demolition of which would be
enormous. The saturation flow of the proposed geometric
design was computed Eq. (1) and results is summarised in
Table 11.
Design of proposed phase plan: A 4-phase plan was
proposed to replace the existing 5-phase plan with the
analysis as shown in Table 12.
From Table 12, the sum of the critical flow ratios for
the new phase plan is given by:
2843
Res. J. Appl. Sci. Eng. Technol., 4(17): 2839-2845, 2012
Table 12: Signal phase, actual capacity and group lanes
Critical volume Saturation
(max hourly
flow
Phase
Movt
volume)(v)
rate(s)
1
Through traffic
689
3066
from sango
Through traffic
619
3431
from post office
2
Through traffic
164
3725
from amilegbe
Through traffic
519
3422
from sabo oke
3
LT from amilegbe
829
3725
4
Flow
ratio
(v/s)
0.225
Proposed
green
time
24
g/C
0.279
0.180
0.044
C = sg/C
capacity
oflane group
855
0.152
16
0.186
692
0.223
23
0.267
994
0.064
7
0.081
913
277
3422
3431
0.059
0.064
LT from sango
68
3066
0.022
Y = 0.225 + 0.152 + 0.223 + 0.064 = 0.664.
Since = 0.664 ‹ 1, it implies that the proposed intersection
geometry is adequate.
Determination of optimum cycle length and signal
settings: The main consideration in selecting cycle length
should be that the least delay is caused to the traffic
passing through the intersection. The optimum cycle
length (Co) proposed is obtained using Eq. (6) (Kadiyali,
2005):
OK/
under saturated
636
0.223
202
220
Remarks
OK/
under saturated
957
0.152
LT from sabo oke
LT from post office
Co = (1.5L+5) /1-Y sec
Flow ratio
for critical
lane group(v/s)cr
0.225
OK/
under saturated
OK/
under saturated
248
Table 13: Summary of timings of proposed signalization scheme
Phase
1
2
3
4
Green time (sec)
24
16
23
7
Total lost time (sec)
16
Cycle length (sec)
86
Table 14: Level of service in terms of delay for proposed phase plan
g c
X
d1
d2
PF d (sec)
Phase v/scr
iv
1
0.225 689 24 855
0.81 28.9 8
1 37
2
0.152 519 16 636
0.82 33.6 11.3 1 44.9
3
0.223 829 23 994
0.83 29.6 8
1 37.6
4
0.064 220 7 277
0.79 38.77 20
1 59
LOS
D
D
D
E
Cycle Length, Co = g1 + g2 + g3 + g4 + L = 86 sec
= 24 + 16 + 23 + 7 + 16 = 86 sec
(6)
where,
Table 13 gives the summary of the proposed design
parameters.
Co = Optimum cycle length (sec)
L = Total lost time per cycle (sec)
Y = y1+ y2 +yn
and y1, y2,...,yn are the critical flow ratio for phases
1,2,...,n, thus with L = 16 sec and Y = 0.664:
Co = (1.5*16+5)/1-0.664 = 86 sec
Appraisal of appropriateness of the proposed signal
phasing: Comparison of the road capacity (c) with the
critical maximum hourly flow (v) in each phase
movements in Table 14 shows that the proposed phase
plan is better than the earlier or existing operation. The
new level of service is D (Table 14) as against the F now
existing (Table 8).
The critical v/c ratio for the intersection (Xc) for
proposed phase is given as:
Xc = 3(v/s)cri*(Co/Co-L)
(7)
The automatic traffic signal scheme operating at
Maraba intersection, one of the intersections on the first
priority arterial in Ilorin, Nigeria was evaluated with
following conclusions and recommendation:
where,
Co = Optimum cycle length
L = Total lost time
C
Thus Xc = 0.664*86/(86-16) = 0.82.
Allocation of green time to each phase is obtained
from Eq. (8) and the result shown in Table 13.
g = v/scri*C/ Xc
CONCLUSION AND RECOMMENDATIONS
C
(8)
2844
The signalised traffic control operate at a five
phasing scheme with a cycle length, average start up
and lost time per phase of 120, 2.54 and 4.0 sec,
respectively
The existing traffic signal operation is inadequate
because the junction delays at all the four approaches
indicated LOS F at peak period
Res. J. Appl. Sci. Eng. Technol., 4(17): 2839-2845, 2012
C
C
The sum of the existing critical flow ratio in each of
the five phases is greater than one which implied that
the intersection geometry is inadequate
There was the strong need to redesign the junction
for a more efficient traffic control at the intersection.
Consequently,
C
C
C
A 4-phase traffic signal control scheme with an
optimum cycle length of 86 sec should be used at the
intersection for an enhanced LOS D to operate
The addition of one lane each to Amilegbe, Sango
and Sabo-Oke approaches is recommended while
Further studies should be carried out on the
signalization schemes in use in other intersections in
the metropolis.
REFERENCES
Adeleke, O.O., 2010. Empirical modelling of delays at
traffic warden controlled urban intersections: Case
study of Ilorin, Nigeria. Ph.D. Thesis, University of
Ilorin, Ilorin, Nigeria, Unpublished.
Adeleke, O.O. and Y.A. Jimoh, 2011. Sampling of
intersections for traffic delay study in an African sub
region urban city. Epistemics Sci. Eng. Technol.,
1(3): 131-137.
Federal Highway Administration, 2009. National Manual
on Uniform Traffic Control Devices for Streets and
Highways (MUTCD). Washington, D.C., USA.
http://mutcd.fhwa.dot.gov/
Highway Capacity Manual, 1994. Special Report 209,
National Academy of Science. National Research
Council, Washington D.C., USA.
Highway Capacity Manual, 2000. National Research
Council. Washington D.C., pp: 27.
Kadiyali, L.R. and N.B. Lal, 2005. Principles and
Practices of Highway Engineering: (Including
Expressways and Airport Engineering). 4th Edn.,
Khana Publishers, Delhi, pp: 835, ISBN:
8174091653.
McShane, W.R., R.P. Rogers and E.S. Prassas, 1998.
Traffic Engineering. Prentice Hall, Upper Saddle
River, New Jersey, pp: 714.
Ndoke, P.N., 2006. Traffic control by traffic warden in
Minna, Niger State, Nigeria. Leonardo J. Sci., (8):
53-60. Spencer, R.G., A. Chalterjee and J.B.
Humphrey, 1982. Traffic analysis for large
construction projects. Transp. Eng. J., 108(6): 570584.
2845